CALENDAR MONTHS.-The year is divided into twelve calendar monthsJanuary, February, March, April, May, June, July, August, September, October, November, December. These are of unequal length : Thirty days hath September, LEAP YEAR. When the two last figures in the number of the year are divisible by four, without a remainder, it is a leap year; when this is not the case, the remainder shows how many years have elapsed since the last leap year. To this there is one exception, as the exact centuries are not leap years, except when the number of centuries is divisible by four without a remainder. Thus 1700, 1800, 1900 are common years, and 2000 a leap year. SEASONS.-Spring commences March 21; Autumn, September 23; Summer, June 21 (the longest day); Winter, December 21 (the shortest day). + plus, Latin for more, signifies that the sum of the numbers between which it stands is to be taken. Thus 6+ 8 (which is read 6 plus 8) equals 14. minus, Latin for less, shows that the number written after it is to be subtracted from that which goes before. Thus 9 6 (which is read 9 minus 6) = 3. x into, times, or multiplied by, placed between two numbers, indicates that the one is to be multiplied by the other. Thus, 5 x 25, (which is read 5 into 25) = 125. divided by, or by, denotes that the number which stands before it is to be divided by that which follows it. Thus 82 (which is read 8 4. 2)8,, are expressions having the same import. by 2) = = equal to, signifies that the expressions between which it stands are equal. Thus, 8 + 2 : 10,8-2 6,8 x 2 16, 8 ÷ 2 = 4. These are respectively read, 8 plus 2 equals 10, 8 minus 2 equals 6, 8 into 2 equals 16, 8 by 2 equals 4. is to, denotes a ratio. Thus, 108: 144 (which is read 108 is to 144) denotes the ratio of 108 to 144. This is equivalent to 1, meaning that 108 is of 144. The sign is probably a corruption of divided by. :: as, indicates the equality of two ratios or a proportion. Thus, 15 20 21 28. This is read 15 is to 20 as 21 is to 28. The sign :: is probably a corruption of equal to. = 15 20: 21: 28 is the same as 15 ÷ 20 = 21 ÷ 28 or 15 = 21. شد or the radical sign, is used to express that the square root of a number is to be extracted, or to indicate, without extracting, the square root. It is read simply root. Thus 49 7., &c. denote that the cube, fourth, and fifth roots respectively are to be extracted. 1 2 3 4 &c., placed to the right of numbers are called their indices, because they point out the powers of the quantities. Thus 42 means 4 × 4, or 4 multiplied by itself, and is read 4 square; 43 means 4 × 4 × 4, and is read 4 cube. () { } [ ] are brackets indicating that all the numbers they include are to be treated as though forming one quantity. Thus, (3-1) 4 = 42 = 2. > greater than, denotes that the number which precedes is greater than that which follows the sign. Thus 9 > 3 signifies that 9 is greater than 3. < less than, denotes that the number which precedes is less than that which follows the sign. Thus 3 < 9 signifies that 3 is less than 9. 18><1 according as > <. This is read, fifteen sixteenths is greater or less than sixteen seventeenths according as two hundred and fifty-five 272ths is greater or less than two hundred and fifty-six 272ths. ..therefore. *.* since. |